High internal phase o/w emulsions have been investigated with respect to stability. A series of aliphatic hydrocarbons were used as the oil component. By matching the refractive index of both phases, transparent, concentrated emulsions were produced and these emulsions were found to have the highest long-term stability. The long-term stability of transparent emulsions is attributed to a minimum in free energy at the equilibrium thickness, which, in turn, is related to a reduced attraction over the thin aqueous lamellae. Another factor that contributes to the stability is the absence of the destabilizing mechanisms commonly encountered for ordinary emulsions and foams.